目的 比较幼年鼠和成年鼠牙周组织骨保护素（Ospeoprotegerin, OPG）信使RNA（MRNA）表达的不同，以探讨增龄因素影响牙周组织改建的分子机制。方法 以4周（幼年鼠）和24周（成年鼠）雄性大鼠右上第一磨牙的牙周膜和邻近牙槽骨为实验对象，利用OPG多相寡核苷酸探针原位杂交检测实验部传OPG mRNA的表达。结果1. 幼年鼠近牙周膜的牙槽骨面可见破骨细胞和相应的骨陷窝；2. 成年鼠牙刷膜内细胞的OPG mRNA表达高于幼年鼠；3. 鼠牙槽骨绀织中，成年鼠和幼年鼠骨髓腔内均有OPGmRNA表达阳性的细胞，但成年鼠中的表达明显高于幼年鼠；结论 增龄因素使牙用组织内OPG表达明显增强，提示幼年的牙周组织较成年的牙周组织有较强的骨改建能力。

Mechanical strain applied to bone leads to bone remodeling. In the oral cavity, it is unclear how such mechanical force applied to move teeth orthodontically induces alveolar bone remodeling. It is known that osteoclasts are the only cells that are responsible for bone resorption, while the formation and activity of osteoclasts are regulated by osteoblasts. So it is believed that osteoblasts play an important role not only in bone formation but in bone remodeling as well. Therefore, the purpose of this study was to examine the effect of mechanical force on human periodontal ligament (PDL) cells and whether they express osteoblastic characters in vitro. Methods: Human PDL cells cultured in vitro were loaded with intermittently stretching force for 24 hours. The expression of alkaline phosphatase (ALP), osteocalcin (OCN) and osteoprotegerin (OPG) were detected at mRNA and protein levels at 0, 2nd, 4th, 6th, 12th, 24th hours after intermittent force loading. Results: Without any stimulation, ALP and OPG mRNA expressions were detected in human PDL cells by in-situ hybridization, but not that of OCN mRNA. ALP mRNA signal was up-regulated and that of OPG was down-regulated by mechanical force within 24 hours. OCN mRNA expression was induced by mechanical force in the late phase of the 24-hours loading cycle. The changes in secreted proteins showed similar results with those seen at the mRNA level. Conclusion: Human PDL cells express osteoblastic phenotypes under intermittent force loading and play a role in alveolar bone remodeling.

Summary The receptor activator of nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are important bone metabolism molecules, which directly control osteoclastogenesis. Periodontal ligament (PDL) cells play a vital role in maintaining the homeostasis of periodontal tissues, releasing cytokines to affect bone metabolism. The purpose of this study was to investigate the expression of OPG and RANKL in cultured human periodontal ligament cells (hPDLCs) derived from permanent teeth and the expression change after stimulation by 1a, 25-dihydroxyvitamin D3 (1a,25(OH)2vitD3), a kind of bone resorption promoter. HPDLCs were cultured in the presence or absence of 10 8 M 1a,25(OH)2vitD3 in vitro. The expression of mRNA for OPG and RANKL in hPDLCs during 6 days'culture was examined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The level of secreted OPG protein in the culture medium during 6 days'culture was detected by enzyme-linked immunoabsorbent assay (ELISA). The result showed that OPG and RANKL were expressed by hPDLCs. OPG expression was downregulated by 10 8M 1a,25(OH)2vitD3 in a time-dependent manner, while RANKL mRNA was up-regulated. The ratio of OPG/RANKL was decreased. In conclusion, our findings suggest that hPDLCs may regulate the alveolar bone metabolism through the OPG/RANKL system.

目的 核心结合因子Cbfal是决定间充质干细胞向成骨细胞系分化的特异性转录因子，本研究观察人牙周膜细胞在间歇性牵张力作用下Cbfal mRNA的表达变化。方法 系列酶消化法培养人牙周膜细胞，采用体外细胞加力装置施加间歇性牵张力，半定量RT-PCR反应检测cbfal mRNA在加力不同时间点的表达。结果 正常人牙周膜细胞在不受力的情况下cbfal mRNA有微弱表达，加力后表达增强，并具有时效性。结论 间歇性牵张力诱导人牙周膜细胞向成骨方向分化，而Cbfal则在机械力诱导成骨分化的启动阶段发挥作用。

目的 研究人牙周膜细胞骨保护索 (osteoprotegerin, OPG) 及破骨细胞分化因子 (receptor acti-vator nuclear factor kappa B ligand. RANKL)信使RNA (messenger RNA, mRNA) 的表达。方法 系列酶消化法体外培养人牙周膜细胞，逆转录聚台酶链反应 (reverse transcription-potymerase chain reaction, RT-PCR) 检测细胞OPG和RANKL两种骨代谢因子的表达。结果 正常人牙周膜细胞在mRNA水平表达OPG和RANKL。结论 人牙周膜细胞表达OPG和RANKL参与骨组织代谢。这一结论为进一步研究人牙周膜细胞在机械力作用下参与骨改建的机理打下基础。